Numerous techniques have been used to mark liquid hydrocarbon products with the aim of identifying their source and their integrity; they typically involve the incorporation of small quantities of additives or markers in the hydrocarbon. The detection of the markers can be carried out by a certain number of standard analytical techniques such as colorimetry, IR, UV or UV-Visible spectroscopy, mass spectrometry, atomic adsorption spectrometry, gas chromatography and/or liquid chromatography (some of these detection and analysis techniques being optionally coupled together). When a liquid hydrocarbon such as crude oil, an oil base originating from the refinery, a motor fuel or other fuel, containing a marker is accidentally spilt into the environment (for example hydrocarbons leaking from storage tanks, service-station tanks, pipelines etc.), the detection of the marker allows identification of the source of the hydrocarbon.
Moreover, the presence and the concentration of the additives for improving performance incorporated in the motor fuels and other fuels can be deduced by measuring the concentration of the marker added to either the motor fuel or other fuel, or to the additive or package of additives. The marked motor fuel or other hydrocarbon fuel can be checked throughout its distribution network in order to verify its integrity. It can thus be ensured that the motor fuel or other fuel has not been subject to contamination or dilution with other liquid hydrocarbons, which also makes it possible to verify that there is no under- or overdosing of the commercial motor fuel or other fuel with additives. When a marker is included in the package of additives in a given quantity, the concentration of the package in the motor fuel or other hydrocarbon fuel can be deduced by determining the quantity of marker in the final motor fuel or other hydrocarbon fuel by implementing a reliable and precise analysis technique.
Radioactive markers based on tritium, iodine 131, or sulphur 35 have been used for tracing crude oil and motor fuels in pipelines and in storage facilities. Essentially for tax reasons, each type of motor fuel or other fuel intended for the general public has a specific marker added to it, called a “customs tracer”, which is generally a specific dye added in a quantity determined by the regulations of the marketing country.
U.S. Pat. No. 4,141,692 describes the use of chlorinated hydrocarbons having at least 3 chlorine atoms, at least two carbon atoms and an atomic ratio of Cl/C of at least 1 to 3 as hydrocarbon markers. Detection of these markers is carried out by an electron capture detector after separation by gas chromatography. The use of chlorinated hydrocarbons as markers of motor fuels and other liquid hydrocarbon fuels has drawbacks, in particular a certain toxicity (chlorine gas release and/or increased emissions of chlorinated hydrocarbons potentially generating greenhouse gases).
U.S. Pat. No. 4,209,302 describes the use of 1-(4-morpholino)-3-(alpha or beta-naphthylamino) propane at a rate of 0.5 to 12 ppm as marker for gasoline-type motor fuels. These markers do not dye the gasoline; in order to detect them, it is necessary to carry out a chemical extraction followed by a treatment with diazotized 2-chloro-4-nitroaniline which leads to a pink-coloured solution, a colour that can be measured by colorimetry. The major drawback of this detection technique is the preliminary chemical extraction step which can lead to increased measurement errors.
FR Patent No. 2 212 390 or U.S. Pat. No. 3,862,120 describe diazo dyes for liquids which are not miscible with water, in particular the petroleum motor fuels and a process making it possible to quantitatively detect their presence in said liquids by IR adsorption or by thin layer chromatography. U.S. Pat. No. 5,234,475 proposes using as markers of liquid hydrocarbons (gasoline, diesel, jet fuel etc.) one or more fullerenes in quantities ranging from 0.01 to 100 ppm, which can be detected by mass or UV-visible spectroscopy. As the manufacture of the fullerenes is not currently really possible on an industrial scale, these molecules are much too expensive to be incorporated in motor fuels and other convenience fuels intended for the general public.
EP Patent No. 512 404 describes the use, as markers of liquid hydrocarbons, of chemical compounds having an aromatic ring substituted by 2 NO2 groups and an amide or ester group which can be detected by gas chromatography. These markers can be incorporated into the motor fuel directly or via the package of additives. These compounds are hydrolyzed in the presence of traces of water in the hydrocarbon, rendering their use unreliable for the marking and precise quantitative detection of the motor fuel.
EP Patent No. 1 699 907 describes packages of additives for motor fuels or lubricants which comprise anthraquinone derivatives as markers and the use of these packages in motor fuels and lubricants. EP Patent No. 1 816 181 describes markers for ethanol motor fuels which are substituted aromatic compounds, having an axis of three-fold symmetry and containing N, O, P, B which can preferably be used between 0.01 ppm and 50 ppm by mass in ethanol motor fuels. WO 2010/039152 describes a process for marking motor fuels for authentification, in order to ensure, for example, their origin and/or optional mixtures or dilutions. The chemical nature of the markers is not described in detail; it is only indicated that the markers can be dyes or non-radioactive isotopes.
U.S. Pat. No. 5,984,983 describes the use of carbonyl compounds as markers of motor fuels. These markers can be chosen from ketones, aldehydes, esters including lactones), amides (including lactames and imides, anhydrides and carboxylic acids). The presence of these markers is detected by the IR absorption of the carbonyl functions. The only example relates to a gasoline motor fuel marked with dibutyl phthalate (absorbance peak 1740 cm−1) and acetophenone (absorbance peak 1700 cm−1).